Organic Garlic Research in Colorado; Winter Mulching, Irrigation Systems, Spacing, Scape Removal, and Flame Cultivation

Abstract

The Specialty Crops Program at Colorado State University conducted research of hardneck garlic (Allium sativum ophioscorodon) production on certified organic land at the Horticulture Field Research Center northeast of Fort Collins, Colo., during the garlic growing seasons of 2002–03 and 2003–04. Winter mulches and irrigation treatments were studied during the first season. It was found that garlic that was covered by any type of winter mulch (grass hay, single or double layers of floating row cover) resulted in better yields (higher average bulb weight) than garlic which was not covered at all (ANOVA, F = 2.93, P = 0.034). Yields from sprinkler and furrow irrigation were essentially the same; however, furrow irrigation used nearly 30% more water. Too little water was applied to the drip-irrigated treatment and yield suffered. Our findings suggest that yields are negatively impacted when less than 12 inches of combined precipitation and irrigation are received. During the second season, clove planting spacings of 3, 4.5, and 6 inches, and flame weeding and scape removal effects on yields were studied. The bulbs that grew at a 6-inch spacing were significantly larger than those grown at 3 and 4.5 inches (ANOVA, F = 46.5, P < 0.001). Flame weeding had no significant effects on yields (t-test, P = 0.6) and may be more economical compared to hand weeding depending on fuel costs. Removing the scapes did result in slightly higher bulb weights (t-test, P = 0.06). Removing scapes takes extra labor and may not be worth the time for only slightly higher bulb weights; however, selling the edible scapes may offset the cost and generate extra income.